1. Field of the Invention
The invention relates generally to systems and methods for severing a tube-wire or similar transmission conductor that is disposed in a surrounding tubular.
2. Description of the Related Art
Coiled tubing has become a popular means for running a bottom hole assembly (“BHA”) into a subterranean wellbore. A wireline or tube-wire is sometimes run inside of the coiled tubing when realtime downhole data is required, such as during directional drilling or logging. Tube-wire is a tube that contains an insulated cable that is used to provide electrical power and/or data to the bottom hole assembly or to transmit data from the BHA to the surface. Tube-wire is available commercially from manufacturers such as Canada Tech Corporation of Calgary, Canada.
In the event that coiled tubing and the associated BHA become stuck in the wellbore, it is common practice to pump a ball or plug down through the coiled tubing in order to disconnect the BHA from the coiled tubing. If this fails to free the coiled tubing, then the contingency is to kill the well, cut the coiled tubing at the surface, and run a chemical cutter on wireline down through the coiled tubing in order to retrieve the coiled tubing from the well. If this problem occurs with TeleCoil, then it is necessary to retrieve the tube-wire before running the chemical cutter. The tube-wire in a TeleCoil string is comparatively weak compared to conventional braided cable, and using a tensile shear release mechanism in the BHA for the tube-wire is considered unreliable. Accordingly, the TeleCoil BHA incorporates a ball operated tube-wire release mechanism to facilitate retrieval of the tube-wire. There is no contingency available in the event of a failure of this mechanism. Conventional drop bars and “go devil” devices that are used to sever slickline rely upon gravity to be delivered to a point wherein they can sever the slickline. They are unsuitable for use in horizontal or deviated wellbores.